A few weeks ago I was eating nachos with a bunch of retired (and one still-working) powertrain engineers.
The conversation turned to motor oil. They were shaking their heads and clucking with disapproval. Everything the guy in the video says in this video was echoed by my former work friends.
It was their collective belief that as soon as one manufacturer specified 0W-20, all of the other manufacturers pressured their engineers to also approve that viscosity.
For the record, the first number is the viscosity at low temperature and the second number is the equivalent of the viscosity the higher number would be at that temperature. That is, at low temperatures 0W-20 acts like 0W oil and at higher temperatures the oil has the same viscosity that single-viscosity 20W would have at that temperature.
Lubrication scientists (tribologists) achieve the dual-viscosity through the addition of small amounts of chemicals with molecules that look like your closed-fist when cold but then open up like your hand when hot, thereby making the fluid thicker. Over time, that additive becomes less effective and the oil slowly reverts back to the lower number at all temperatures.
The most sensitive part of the engine is typically the camshaft-lifter contact and it is worst when the engine is hot and the engine RPM is low. Most automotive engines now have roller-lifters interacting with the camshaft. Very few "small engines" use that technology.
I don't mean to be a kill-joy, but I see no real-world downside to running 10W-30 year round. You might lose a tiny fraction of a mile-per-gallon in fuel economy but that is chump-change compared to the cost of replacing an engine or being forced to buy a replacement vehicle. The manufacturer might claim that using the higher viscosity invalidates the warranty but IMHO using the higher viscosity oil reduces the likelihood of ever needing the warranty.
I have been using synthetic 5-40 oil for my diesel F350, replacing every 5000 miles. If this is sub-optimal, I would very much like to know. Diesel engines are incredibly expensive, and it's not like the fuel efficiency has much room get worse.
ReplyDeleteI don't have the expertise to answer that.
DeleteOne issue with diesels involves fast shutdowns and fast start-ups.
The problem with running a turbo diesel hard and then shutting down without letting it idle for a minute or two is that the turbo housing and vanes are so hot they glow. A minute or two of idling allows the heat to be passed to the coolant and not just absorbed by the surrounding metal...and the oil in the bearings.
The other side of the issue is that it takes a few seconds to ensure that oil fills the bearing spaces at start-up.
I know that I talked around your question, but that is the best I could manage.
Check out bobistheoilguy, and think about having your oil tested by one of the labs before changing it next time. They might tell you you can extend the interval.
DeleteJim_R
Appropriate motor oil viscosity is a function of clearances within the engine. As manufacturers have reduced clearances and increased the stability of clearances, lower viscosity oils have been required. Using thick oils in close tolerance engines results in lubricant starvation. Using correct, low viscosity oils also reduces fuel consumption, significantly.
ReplyDeleteOverhead cam timing chains are now the most wear critical parts in modern IC engines (both SI & CI), despite forced lubrication. Lifter/lobe interface wear has been greatly reduced through the miracles of 1930's metallurgy, properly applied.
EP additives are being removed from motor oils due to their detrimental effects on catalytic convertors. The latest technology is molybdenum dialkyl dithiocarbamate (MoDTC) and its chemical analog titanium dialkyl dithiocarbamate. It is likely that IC engines in the next decade will be limited to 8 maximum weight oils and 300,000 mile longevity will become the norm.
"...1930's metallurgy, properly applied..."
DeleteKey words: "properly applied". Pintos had massive camshaft issues in their 1970-1980 camshafts. The Triton engine had some of the same issues 2004-2014.
Cast irons tend to have very wide "tolerances" for microstructure and chemistry while induction hardening processes tend to be fussy about coarseness of the grain size. Sometimes the two interact and the process goes into the ditch.
I have to confess that most of my information is circa 1990-1995, so maybe things have changed.
Cast irons are not much used in transportation IC valve trains anymore, with the exception of light aircraft piston engines. And those use chilled cast iron, a special beast, due to the expense of FAA requalification..
DeleteCarburized chromium steels - 5120, 16MnCr5 Scr420 - are the camshaft lobe/lifter norm today. Shape is every bit as important as lubrication and materials. Valve guides are ferrous powder metallurgy, akin to oilite but harder. Valve seats are also ferrous powder metallurgy, but contain very hard ceramic particles. With halfway decent heat management and lubrication, today's IC valvetrains should go 300,000 miles - with the possible exception of timing chains.
I am not able to comment on Ford's valvetrain engineering.
This. My Toyota dealer told us why they recommend lower viscosity oil is because of the increasingly smaller tolerances they design in to modern engines. Too thick of an oil and some parts could be left inadequately lubricated...especially in cold weather.
DeleteSo why do many of the manufacturers specify thicker oils for vehicles not sold in the United States? Same engines. Same equipment makes them. It sounds like dealers making up stories to make a bad decision sound like a virtue.
DeleteI bought a 2-year old Civic off the dealer lot, and did not believe him when the salesman said 10k miles between oil changes. Service manager happened to be nearby, he grabbed him, we talked for a few minutes. Story from this fellow was, the newer engines are so tightly manufactured, to such tight tolerances, use 0w20 full synthetic, every 10k, it'll be OK.
ReplyDeleteI've put ~220k miles on that thing, done 22 oil changes myself, 0w20 full syn every time. Nary a tick, nor an issue.
Now that's a Honda 1.8l gas engine, I can't comment beyond that. The Kubota tractor gets Rotella, and nothing else will ever go in any of my diesel motors.
Yup... thicker oil is better than the 0w20. 5w30 or 10w30 from a good refiner and change it regularly. And change the damn filter too!!! I've seen so many service schedules that specify a filter change every other oil change... put a fresh filter and new oil in it frequently. It's the best extended warranty you can put on a vehicle.
ReplyDeleteIf you're in doubt change the fluid. It's cheaper than an engine. Or a ps pump or a transmission or any other lubricated system. And let that turbo cool before you shut it down. Several minutes at idle if you've been working her hard. The turbo bearings will thank you, your wallet will thank you and the next owner will thank you. Fresh filters and fluids make mechanical equipment live longer.
[end rant]
I have been running synthetics since the mid-90s. We did a tear down on my Chevy 350 with over 225,000 miles on it and the internals were all good. The injectors were shot, as was the wiring, but not unexpected.
ReplyDeleteThicker oil is a better thing...UP TO A POINT.
ReplyDeleteuse 5w 30 instead of 0w-20? Probably better.
Go to 10W40 and you might have issues with oil starvation and other lubrication flows details. Plus the filter may or may not be in bypass, leading to other issues.
Synthetics are another thing. You can't compare paraffin based oils from the 1960's to modern synthetics, they cling more, they flow better, they have significantly greater lubricity.
Thicker isn't (always) better.
It all comes down to the films that protect your moving engine parts from each other.
No one ever was unhappy that they let a turbo cool for 5 minutes either.
My 2025 Mazda cx 5 naturally aspirated 2.5 l specifies 0-20 oil,
ReplyDeleteIn North America. For other countries it specifies 5-30.
My takeaway from this is they were trying very hard to meet a fuel economy standard.
When I bought my first car 61 years ago, a 1950 Chevy, I used 10W30 in it because that's what my Dad always used in cars, trucks, tractors and small engines. And I have done the same ever since in my cars, trucks, tractors and small engines and it always worked fine. But sometimes things change, especially all things of late, so I'll pay attention concerning that new stuff.. ---ken
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